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[2am Omega]

97 R plate Omega Elite 2.5 V6 Auto Petrol engine ran smoothly .. then suddenly juddering, especially at lower revs, with reduced power and petrol consumption almost doubled, typically 14-18 mpg. Juddering quite noticeable as soon as auto changes up to top gear at 2000rpm at just under 50 mph. Possibly not firing on all 6 cylinders? Or fuel flow .. jets/filter?

Burst SAI hose replaced so vacuum resolved ..  and breather hose .. but still juddering and poor mpg. MOT garage did quick review - thinks may be misfiring? - says exhaust unlikely to be the cause, even though rear box innerds emptied.

Paperclip test shows no faults.

Wondering if HT plugs/leads or Dis Pack could be the problem. How can I test these? Even accessing the plugs seems difficult.

Suggestions welcome please on possible causes to explore.

[MutantCav]

Check plug wells for oil in them...maybe your cam cover gaskets are leaking...have you lost any oil??

[Varche]

Sounds like it may be your DIS pack. They aren't easy to change as it is down the back of the engine. Plenty of info on the site if you do a search. I had the same symptoms and changed plug leads first. If you have been losing water a little it could be the Heater bypass valve and that dribbles nicely onto your DIS pack.

It could be your cam cover gaskets gone. I had that problem too on same year car etc as yours. They aren't easy to get at but pull at least one lead off both banks to check. Again loads of info on the site for changing the gaskets IF that is the problem. Use only genuine VX gaskets.


Someone else will be along with suggestions for how to test to narrow it down.

varche

[Gaffers]

Sounds like it may be your DIS pack. They aren't easy to change as it is down the back of the engine. Plenty of info on the site if you do a search. I had the same symptoms and changed plug leads first. If you have been losing water a little it could be the Heater bypass valve and that dribbles nicely onto your DIS pack.

It could be your cam cover gaskets gone. I had that problem too on same year car etc as yours. They aren't easy to get at but pull at least one lead off both banks to check. Again loads of info on the site for changing the gaskets IF that is the problem. Use only genuine VX gaskets.


Someone else will be along with suggestions for how to test to narrow it down.

varche

seconded  

[2am Omega]

Thanks guys.

I'm not aware of losing oil or water but I will check in daylight.

Is there an easy way to test and check the existing Dis Pack in situ? It sounds like a complicated job and an expensive device to replace unless there is certainty of the need to do so.

[feeutfo]

def miss fire. No test for dis afaik. I think its a case of easiest cheapest first. Check the wells for oil first. If no oil then how old are the plugs? 40k life i think, any black lines or tracks on the insulators. If they are ok and not due then would suggest dis pac esp if its been sprayed with water from a leaking hbv, screen seal or scuttle dripping. But its a gamble that the leads are not to blame, how do they look are they genuine, any splits in the rubber boots?

[2am Omega]

There is no loss of oil as far as I can see. Dipstick is normal, never any oil under car, and none on top of sloping engine area around plug caps .. are those the "wells" ?

Also apparently no loss of cooling system water. Please confirm where is the heater bypass valve and what does it look like? Is it easy to see if this has leaked?

I have bought new plugs but accessibility is terrible, especially on nearside. Do I need a special plug spanner to unscrew them? .. even the offside plugs are so deep, almost like a mineshaft !!

Can I try to locate any problem cylinder HT by removing plug caps, one at a time, to see if engine runs more unevenly on each cylinder?

[Varche]

You may not have seen water loss from the heater bypass valve as it is conveniently tucked away high up at the back of the engine under the scuttle. You may just have been topping up the header tank from time to time.

Have a search on this site for how to change a DIS Pack. It is fiddly but not horribly difficult. You need to get the old one off to see which one you need to buy. From memory mine could have been one of two types.

varche

[2am Omega]

I have not needed to top up my cooling system water for over a year, and negligible amount over almost 4 years. It is at normal level now. Maybe that suggests I'm lucky in avoiding a leaking heater bypass valve .. and maybe not the Dis Pack if it has escaped a hot shower?

Perhaps I should try to check the plugs and HT leads first? Could someone offer guidance please .. see my post above.

[feeutfo]

if there is oil in the plug wells(or mine shafts) its very likely you wont notice the oil loss on the dip stick. Only way is to look, which you will when you change the plugs obviously. Pass side is the difficult side and involves removing/pulling to one side the cable tray, it aint that hard tho. Blow off any crap to stop it falling down the well and into the cylinder when the plugs come out. Inspect the plug leads and caps for any damage while your there. Look for any black lines on the white bit of the plugs and any white/grey residue on the rubber thats left when the spark escapes. Some say any spark escape can be seen at night or when dark, hold the bonnet down and look through the gap. You never know.

Start with the spark plug end and if all is well then you need to inspect the dis pac and that end of the leads. See how you go, hopefully its just the plugs and you wont have to look any further. Hth

[feeutfo]

ps there is as standard, a brown plug lead puller attached to plug no.1 if its still there.

[2am Omega]

Checked in the dark .. I cannot see any sparking around plugs or HT leads.

BUT ..

I was pressing down on each plug cap to ensure good connection.
Just found something which may be part of my problem .. one spark plug may be loose.

There is a rattling sound when I press on the plug cap .. this is the same first plug that a friend tried to remove to change plugs, but he gave up because of accessibility problems down those awful "mineshafts". Problems with his plug socket reaching down there. But it looks like he did loosen that plug without realising.  

Do you think this could be the cause of the juddering and lumpy running with poor fuel consumption?

[feeutfo]

Right, had a look at this for Mr 2am today and must say i am a little bemused. It was running a little lumpy when we drove it as he says. It also feels strangled and vibey. Changed the plugs, and found some oil in the wells, but nothing major, it was not as high in the well so as to reach the hight of the rubber boots on the plug caps for instance.

Plugs changed and it does sound like a subaru impreza, but the engine does not leap around in the engine bay like my old car did when one cylinder went down due to a split rubber on the plug cap. compared to that its quite smooth. Pulled a couple of plug leads while it was running, ouch, and this made little difference to the rough running. 1 and 5 barely made any dirrerence when pulled, but 3 made a slight difference.

The plug cap on cylinder 6 had a major portion of rubber missing, assuming 1 5 and 6 aint working why isnt the engine leaping around like a nutter??

Took the scuttle off to peak at the dis pac, and with both feet off the floor i could see down onto it. No visible sign of damage cracks or splitting that i can see without removing it.

also the vac system aint right, not a peep from either multi rams and there is a leak from a small pipe the back, taped that up, with a busted elbow connector on the vac tank on the inlet trumpets.

personally, if it was mine i would change the leeds, and fix the the vac system, although i have little experience of that, and go from there.

Just want to run it by you lot, and see what you think, opinions please ladys and gents. TA

ps some other monkeys have been at this car, i will leave that Mr 2am
to discuss, perhaps on another thread to save confussion, we just need to sort this out for him for now, he really needs a reliable car.

pps took some pics will post up tonight.

[feeutfo]

any second opinions please guys?

Cheers

[feeutfo]

buggered lead on pot6


the missing bit


vac tank and broken off connector to elbow